Fibers comprising polyesteramide copolymers for drug delivery

ABSTRACT

The present invention relates to fibers comprising a polyesteramide (PEA) having a chemical formula described by structural formula (IV), wherein m+p varies from 0.9-0.1 and q varies from 0.1 to 0.9, m+p+q=1 whereby m or p could be 0, n is about 5 to about 300; (pref. 50-200), —R 1  is independently selected from the group consisting of (C 2 -C 20 ) alkylene or (C 2 -C 20 ) alkenylene and combinations thereof; —R 3  and R 4  in a single backbone unit m or p, respectively, are independently selected from the group consisting of hydrogen, (C 1 -C 6 )alkyl, (C 2 -C 6 )alkenyl, (C 2 -C 6 )alkynyl, (C 6 -C 10 )aryl, —(CH 2 )SH, —(CH 2 ) 2 S(CH 3 ), —CH 2 OH, —CH(OH)CH 3 , —(CH 2 ) 4 NH 3 +, —(CH 2 ) 3 NHC(═NH 2 +)NH 2 , —CH 2 COOH, —(CH 2 )COOH, —CH 2 —CO—NH 2 , —CH 2 CH 2 —CO—NH 2 , —NH—CH 2 CH 2 COOH, CH 3 —CH 2 —CH(CH 3 )—, (CH 3 ) 2 —CH—CH 2 —, H 2 N—(CH 2 ) 4 —, Ph-CH 2 —, CH═C—CH 2 —, HO-p-Ph-CH 2 —, (CH 3 ) 2 —CH—, Ph-NH—, NH—(CH 2 ) 3 —C—, NH—CH═N—CH═C—CH 2 —. —R 5  is selected from the group consisting of (C 2 -C 20 )alkylene, (C 2 -C 20 )alkenylene, alkyloxy or oligoethyleneglycol, —R 6  is selected from bicyclic-fragments of 1,4:3,6-dianhydrohexitols of structural formula (III); —R 7  is selected from the group consisting of (C 6 -C 10 )aryl (C 1 C 6 )alkyl, —R 8  is —(CH 2 )4-; whereby a is at least 0.05 and b is at least 0.05 and a+b=1.

The present invention relates to fibers comprising polyesteramideco-polymers. The present invention also relates to the fibers for use inmedical applications especially for use in the delivery of bioactiveagents.

Biodegradable polyesteramides are known in the art, in particularα-amino acid-diol-diester based polyesteramides (PEA) are known from G.Tsitlanadze, et al. J. Biomater. Sci. Polym. Edn. (2004) 15:1-24. Thesepolyesteramides provide a variety of physical and mechanical propertiesas well as biodegradable profiles which can be adjusted by varying threecomponents in the building blocks during their synthesis: naturallyoccurring amino acids and, therefore, hydrophobic alpha-amino acids,non-toxic fatty diols and aliphatic dicarboxylic acids.

WO2002/18477 specifically refers to alpha-amino acid-diol-diester basedpolyesteramides (PEA) copolymers of formula I, further referred to asPEA-I,

wherein:

m varies from 0.1 to 0.9; p varies from 0.9 to 0.1; n varies from 50 toabout 150;

-   -   each R₁ is independently (C₁-C₂₀)alkylene;    -   each R₂ is independently hydrogen or (C₆-C₁₀)aryl(C₁-C₆)alkyl;    -   each R₃ is independently hydrogen, (C₁-C₆) alkyl,        (C₂-C₆)alkenyl, (C₂-C₆)alkynyl, or (C₆-C₁₀)aryl(C₁-C₆)alkyl; and    -   each R₄ is independently (C₂-C₂₀)alkylene.        PEA-I is a random copolymer comprising m units build upon        alpha-amino acids, diols and an aliphatic dicarboxylic acids,        which are copolymerized with p units build upon an aliphatic        dicarboxylic acid and L-lysine.

WO2007035938 discloses another type of random PEA co-polymers accordingto Formula II comprising at least two linear saturated or unsaturatedaliphatic diol residues into two bis-(a amino acid)-based diol-diesters.

wherein

m is 0.01 to 0.99; p is 0.99 to 0.01; and q is 0.99 to 0.01; and whereinn is 5 to 100; wherein

—R₁ can be independently selected from the group consisting of(C₂-C₂₀)alkylene, (C₂-C₂₀)alkenylene, —(R₉—CO—O—R₁₀—O—CO—R₉)—,—CHR₁₁—O—CO—R₁₂—COOCR₁₁— and combinations thereof;

—R₃ and R₄ in a single co-monomer m or p, respectively, can beindependently selected from the group consisting of hydrogen,(C₁-C₆)alkyl, (C₂-C₆)alkenyl, (C₂-C₆)alkynyl, (C₆-C₁₀)aryl,(C₁-C₆)alkyl, —(CH₂)SH, —(CH₂)₂S(CH₃), —CH₂OH, —CH(OH)CH₃, —(CH₂)₄NH₃+,—(CH₂)₃NHC(═NH₂+)NH₂, —CH₂COOH, —(CH₂)COOH, —CH₂—CO—NH₂, —CH₂CH₂—CO—NH₂,— —CH₂CH₂COOH, CH₃—CH₂—CH(CH₃)—, (CH₃)₂—CH—CH₂—, H₂N—(CH₂)₄—, Ph-CH₂—,CH═C—CH₂—, HO-p-Ph-CH₂—, (CH₃)₂—CH—, Ph-NH—, NH—(CH₂)₃—C—,NH—CH═N—CH═C—CH₂—.

—R₅ is can be selected from the group consisting of (C₂-C₂₀)alkylene,(C₂-C₂₀)alkenylene, alkyloxy or oligoethyleneglycol;

—R₆ can be selected from bicyclic-fragments of 1,4:3,6-dianhydrohexitolsof structural formula (III); cycloalkyl fragments such as1,4-cyclohexane diol derivative, aromatic fragments or heterocyclicfragments such as hexose derived fragments.

—R₇ can be hydrogen, (C₆-C₁₀) aryl, (C₁-C₆) alkyl or a protecting groupsuch as benzyl- or a bioactive agent;

—R₈ can be independently (C₁-C₂₀) alkyl or (C₂-C₂₀)alkenyl;

—R₉ or R₁₀ can be independently selected from C₂-C₁₂ alkylene or C₂-C₁₂alkenylene.

—R₁₁ or R₁₂ can be independently selected from H, methyl, C₂-C₁₂alkylene or C₂-C₁₂ alkenylene.

If in the random polyesteramide co-polymer of Formula (II) m+p+q=1,q=0.25, p=0.45 whereby R₁ is —(CH₂)₈; R₃ and R₄ in the backbone units mand p is leucine, —R₅ is hexane, and R₆ is a bicyclic-fragments of1,4:3,6-dianhydrohexitols of structural formula (III); R₇ is benzylgroup and R₈ is —(CH₂)₄— this polyesteramide is further referred to asPEA-III-Bz. In case that R₇ is H, the polyesteramide is further referredto as PEA-III-H. In case that m+p+q=1, q=0.25, p=0.75 and m=0, wherebyR₁ is —(CH₂)₄; R₃ is (CH₃)₂—CH—CH₂—, R₇ is benzyl, R₈ is —(CH₂)₄; and R₆is selected from bicyclic-fragments of 1,4:3,6-dianhydrohexitols ofstructural formula (III), the polyesteramide is further referred to asPEA-IV-Bz, in case that R₇ is H the polyesteramide is further referredto as PEA-IV-H.

The polyesteramides facilitate the in vivo release of bioactive agentsdispersed in the polymer at a controlled release rate, which is specificand constant over a prolonged period. It is furthermore disclosed thatthe PEA polymers break down in vivo via enzymes to produce naturalα-amino acids among the break down products which are substantiallynon-inflammatory.

However in some medical areas there is a need for polymers and drugdelivery forms such as fibers comprising polymers which degradehydrolytically instead of enzymatically. This need exists for example inophthalmology where the delivery of drugs intra-ocularly is a particularproblem. The eye is divided into two chambers; the anterior segmentwhich is the front of the eye, and the posterior segment which is theback of the eye. In the back of the eye, in the vitreous, less or noenzymes are present such that for example fibers or rods based onenzymatically degradable polyesteramides will not degrade or willdegrade too slow. Any of these two events will compromise the fiberdegradability in-vivo and respectively the fiber as biodegradable drugelution system for medical applications.

There is thus still a need in the art for a fiber as delivery systemcomprising biodegradable polyesteramides which provide for continuousdelivery of bioactive agents over a sustained period of time.

The object of the present invention is therefore to provide fiberscomprising biodegradable polyesteramide copolymers which take away theabove mentioned disadvantages associated with fiber degradation.

The object of the present invention is achieved by providing fiberscomprising a biodegradable poly(esteramide) copolymer (PEA) according tostructural formula (IV),

wherein

m+p varies from 0.9-0.1 and q varies from 0.1 to 0.9

m+p+q=1 whereby m or p could be 0

n is about 5 to about 300;

—R, is independently selected from the group consisting of (C₂-C₂₀)alkylene, (C₂-C₂₀) alkenylene, —(R₉—CO—O—R₁₀—O—CO—R₉)—,—CHR₁₁—O—CO—R₁₂—COOCR₁₁— and combinations thereof;—R₃ and R₄ in a single backbone unit m or p, respectively, areindependently selected from the group consisting of hydrogen,(C₁-C₆)alkyl, (C₂-C₆)alkenyl, (C₂-C₆)alkynyl, (C₆-C₁₀)aryl,(C₁-C₆)alkyl, —(CH₂)SH, —(CH₂)₂S(CH₃), —CH₂OH, —CH(OH)CH₃, —(CH₂)₄NH₃+,—(CH₂)₃NHC(═NH₂+)NH₂, —CH₂COOH, —(CH₂)COOH, —CH₂—CO—NH₂, —CH₂CH₂—CO—NH₂,—CH₂CH₂COOH, CH₃—CH₂—CH(CH₃)—, (CH₃)₂—CH—CH₂—, H₂N—(CH₂)₄—, Ph-CH₂—,CH═C—CH₂—, HO-p-Ph-CH₂—, (CH₃)₂—CH—, Ph-NH—, NH—(CH₂)₃—C—,NH—CH═N—CH═C—CH₂—;—R₅ is selected from the group consisting of (C₂-C₂₀)alkylene,(C₂-C₂₀)alkenylene, alkyloxy or oligoethyleneglycol—R₆ is selected from bicyclic-fragments of 1,4:3,6-dianhydrohexitols ofstructural formula (III); cycloalkyl fragments such as 1,4-cyclohexanediol derivative, aromatic fragments or heterocyclic fragments such ashexose derived fragments.

—R₇ is selected from the group consisting of (C₆-C₁₀) aryl (C₁-C₆) alkyl

—R₈ is —(CH₂)₄—;

—R₉ or R₁₀ are independently selected from C₂-C₁₂ alkylene or C₂-C₁₂alkenylene.—R₁₁ or R₁₂ are independently selected from H, methyl, C₂-C₁₂ alkyleneor C₂-C₁₂ alkenylene whereby a is at least 0.05, b is at least 0.05 anda+b=1.

Surprisingly it has been found that fibers comprising the biodegradablepolyesteramides of formula (IV) in which both L-Lysine-H as wellL-lysine-benzyl are present, (hereinafter referred to as PEA-H/Bz)provide unexpected properties in terms of release and degradation. Ithas been found that fibers comprising PEA-H/Bz co-polymers provide asustained release of bioactive agents and degrade hydrolytically atphysiological conditions via bulk erosion mechanism in contrast with thePEA polymers known in the prior art that degrade only in presence ofcertain classes of enzymes by surface erosion.

The degradation properties of the fibers comprising the PEA-H/Bzco-polymers according to the present invention are markedly differentthan the degradation properties of prior art polymers such as the abovenamed PEA-I, PEA-III, PEA-IV or polyesters for examplepoly-lactide-glycolide copolymers (PLGA) or polylactide (PLLA). It hasbeen found that fibers comprising the PEA-H/Bz co-polymers seem todegrade hydrolytically and mainly via bulk erosion mechanism whereas theknown PEA's degrade mainly via an enzymatic degradation process and viaa surface erosion mechanism.

A further disadvantage in the degradation of for example PLGA and PLLAfibers is the fact that they often result in a pH drop which isundesired because it may influence the stability of the bioactive agentto be released from the fibers trigger inflammatory response. It is wellknown that during degradation of PLGA fibers highly acidic degradationproducts are formed resulting in pH drop. In contrast the pH of thePEA-III-H/Bz fibers does not change under analogous conditions. It seemsthat lysine free carboxylic groups and acidic species generated duringthe degradation are in a right balance to catalyze bond cleavage alongthe polyesteramide chain but not compromising the optimal physiologicalconditions. From experiments it has been found that fibers of PEA-H/Bzdo not show a significant pH drop.

The above findings confirm that fibers comprising the polyesteramides offormula IV in which both L-Lysine-H as well L-lysine-benzyl are presentin a certain ratio provides surprising properties addressing better theneeds of fibers or rods in drug delivery.

In the following embodiments of the present invention n in Formula (IV)preferably varies from 50-200 and a may be at least 0.15, morepreferably at least 0.5, most preferably 0.75, even more preferably atleast 0.8.

In one embodiment the fibers comprising the biodegradable polyesteramidecopolymer according to Formula (IV) comprise p=0 and m+q=1 wherebym=0.75, a=0.5 and a+b=1, R₁ is (CH₂)₈, R₃ is —(CH₃)₂—CH—CH₂—, R₅ ishexyl, R₇ is benzyl and R₈ is —(CH₂)₄—. This polyesteramide is referredto as PEA-I-H/Bz 50% H.

In another preferred embodiment of the present invention the fiberscomprising the biodegradable polyesteramide copolymer according toFormula (IV) comprise m+p+q=1, q=0.25, p=0.45 and m=0.3 whereby a is 0.5and a+b=1 and whereby R₁ is —(CH₂)₈; R₃ and R₄ respectively are—(CH₃)₂—CH—CH₂—, R₅ is selected from the group consisting of(C₂-C₂₀)alkylene, R₆ is selected from bicyclic-fragments of1,4:3,6-dianhydrohexitols of structural formula (II); R₇ is benzyl andR₈ is —(CH₂)₄. This polyesteramide is referred to as PEA-III-H/Bz 50% H.

In a still further preferred embodiment of the present invention fiberscomprising the biodegradable polyesteramide copolymer according toFormula (IV) comprise m+p+q=1, q=0.25, p=0.45 and m=0.3 whereby a is0.75 and a+b=1, R, is —(CH₂)₈; R₄ is (CH₃)₂—CH—CH₂—, R₇ is benzyl, R₈ is—(CH₂)₄— and R₆ is selected from bicyclic fragments of1,4:3,6-dianhydrohexitols of structural formula (III). Thispolyesteramide is referred to as PEA-III-H/Bz 25% H.

In a yet further preferred embodiment of the present invention thefibers comprising the biodegradable poly(esteramide) copolymer accordingto Formula (IV) comprise m+p+q=1, q=0.1, p=0.30 and m=0.6 whereby a=0.5and a+b=1. R₁ is —(CH₂)₄; R₃ and R₄ respectively, are (CH₃)₂—CH—CH₂—; R₅is selected from the group consisting of (C₂-C₂₀)alkylene, R₇ is benzyl,R₈ is —(CH₂)₄— and R₆ is selected from bicyclic-fragments of1,4:3,6-dianhydrohexitols of structural formula (III). Thispolyesteramide is referred to as PEA-II-H/Bz 50% H.

As used herein, the term “alkyl” refers to a monovalent straight orbranched chain hydrocarbon group including methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, tert-butyl, n-hexyl, and the like.

As used herein, the term “alkylene” refers to a divalent branched orunbranched hydrocarbon chain such as —CH2-, —(CH2)2-, —(CH2)3-,—(CH2)4-, —(CH2)5- and the like.

As used herein, the term “alkenyl” refers to a monovalent straight orbranched chain hydrocarbon group containing at least one unsaturatedbond in the main chain or in a side chain.

As used herein, “alkenylene”, refers to structural formulas herein tomean a divalent branched or unbranched hydrocarbon chain containing atleast one unsaturated bond in the main chain or in a side chain.

As used herein, “alkynyl”, refers to straight or branched chainhydrocarbon groups having at least one carbon-carbon triple bond.

The term “aryl” is used with reference to structural formulas herein todenote a phenyl radical or an ortho-fused bicyclic carbocyclic radicalhaving about nine to ten ring atoms in which at least one ring isaromatic. Examples of aryl include, but are not limited to, phenyl,naphthyl, and nitrophenyl.

The term biodegradable” refers to material which is capable of beingcompletely or substantially degraded or eroded when exposed to an invivo environment or a representative in vitro. A polymer is capable ofbeing degraded or eroded when it can be gradually broken-down, resorbed,absorbed and/or eliminated by, for example, hydrolysis, enzymolysis,oxidation, metabolic processes, bulk or surface erosion, and the likewithin a subject. The terms “bioabsorbable” and “biodegradable” are usedinterchangeably in this application.

The term “random copolymer” as used herein refers to the distribution ofthe m, p and q units of the polyesteramide of formula (IV) in a randomdistribution.

As used herein, fibers include also rods or wires.

At least one of the alpha-amino acids used in the polyesteramideco-polymers according to formula (IV) is a natural alpha-amino acid. Forexample, when the R3s or R4s are benzyl the natural alpha-amino acidused in synthesis is L-phenylalanine. In alternatives wherein the R₃s orR₄s are —CH₂—CH(CH₃)₂, the co-polymer contains the natural amino acid,leucine. By independently varying the R₃s and R₄s within variations ofthe two co-monomers as described herein, other natural alpha-amino acidscan also be used, e.g., glycine (when the R₃ or R₄ are H), alanine (whenthe R₃ or R₄ are CH₃), valine (when the R₃ or R₄ are —CH(CH₃)₂,isoleucine (when the R₃ or R₄ are —CH(CH₃)—CH₂—CH₃), phenylalanine (whenthe R₃ or R₄ are CH₂—C₆H₅), lysine (when the R₃ or R₄ (CH₂)₄—NH₂); ormethionine (when the R₃s or R₄s are —(CH₂)₂S(CH₃), and mixtures thereof.

The polyesteramide co-polymers of Formula (IV) preferably have anaverage number molecular weight (Mn) ranging from 15,000 to 200,000Daltons. The polyesteramide co-polymers described herein can befabricated in a variety of molecular weights and a variety of relativeproportions of the m, p, and q units in the backbone. The appropriatemolecular weight for a particular use is readily determined by oneskilled in the art. A suitable Mn will be in the order of about 15,000to about 100,000 Daltons, for example from about 30,000 to about 80,000or from about 35,000 to about 75,000. Mn is measured via GPC in THF withpolystyrene as standard.

The basic polymerization process of polyesteramides is based on theprocess described by G. Tsitlanadze, et al. J. Biomater. Sci. Polym.Edn. (2004) 15:1-24, however different building blocks and activatinggroups were used.

The polyesteramides of Formula (IV) are for example synthesized as shownin scheme 1; via solution polycondensation of para-toluene sulfonatedi-amines salts (X1, X2, X3) with activated di-acids (Y1). Typicallydimethylsulfoxide or dimethylformamide is used as solvent. Typically asa base triethylamide is added, the reaction is carried out under aninert atmosphere at 60° C. for 24-72 hours under constant stirring.Subsequently the obtained reaction mixture is purified via a waterprecipitation followed by an organic precipitation and filtration.Drying under reduced pressure yields the polyesteramide.

Typically, the average diameter of the fibers is between 50 and 1000micrometer. The preferred average diameter depends on the intended use.For instance, in case the fibers are intended for use as an injectabledrug delivery system, in particular as an ocular drug delivery system,an average diameter of 50-500 μm may be desired, more preferably anaverage diameter of 100-300 μm may be desired.

The fibers of the present invention may be used as a delivery system forbioactive agents but also for the delivery of diagnostic aids or imagingagents.

The fibers according to the present invention may comprise one or morebioactive agents. The bioactive agent(s) may be more or lesshomogeneously dispersed within the fibers.

In particular, the bioactive agent may be selected from the group ofnutrients, pharmaceuticals, small molecule drugs, proteins, peptides,vaccines, genetic materials, (such as polynucleotides, oligonucleotides,plasmids, DNA and RNA), diagnostic agents, and imaging agents. Thebioactive agent, such as an bioactive pharmacologic ingredient (API),may demonstrate any kind of activity, depending on the intended use.

The bioactive agent may be capable of stimulating or suppressing abiological response. The bioactive agent may for example be chosen fromgrowth factors (VEGF, FGF, MCP-1, PIGF, antibiotics (for instancepenicillin's such as B-lactams, chloramphenicol), anti-inflammatorycompounds, antithrombogenic compounds, anti-claudication drugs,anti-arrhythmic drugs, anti-atherosclerotic drugs, antihistamines,cancer drugs, vascular drugs, ophthalmic drugs, amino acids, vitamins,hormones, neurotransmitters, neurohormones, enzymes, signallingmolecules and psychoactive medicaments.

The bioactive agents can have antiproliferative or anti-inflammatoryproperties or can have other properties such as antineoplastic,antiplatelet, anti-coagulant, anti-fibrin, antithrombotic, antimitotic,antibiotic, antiallergic, or antioxidant properties. Examples ofantiproliferative agents include rapamycin and its functional orstructural derivatives, 40-O-(2-hydroxyl)ethyl-rapamycin (everolimus),and its functional or structural derivatives, paclitaxel and itsfunctional and structural derivatives. Examples of rapamycin derivativesinclude ABT-578, 40-O-(3-hydroxyl)propyl-rapamycin,40-O-[2-(2-hydroxyl)ethoxy]ethyl-rapamycin, and40-O-tetrazole-rapamycin. Examples of paclitaxel derivatives includedocetaxel. Examples of antineoplastics and/or antimitotics includemethotrexate, azathioprine, vincristine, vinblastine, fluorouracil,doxorubicin hydrochloride (e.g. Adriamycin(R) from Pharmacia AND Upjohn,Peapack N.J.), and mitomycin (e.g. Mutamycin(R) from Bristol-MyersSquibb Co., Stamford, Conn.). Examples of such antiplatelets,anticoagulants, antifibrin, and antithrombins include sodium heparin,low molecular weight heparins, heparinoids, hirudin, argatroban,forskolin, vapiprost, prostacyclin and prostacyclin analogues, dextran,D-phe-pro-arg-chloromethylketone (synthetic antithrombin), dipyridamole,glycoprotein Hb/nia platelet membrane receptor antagonist antibody,recombinant hirudin, thrombin inhibitors such as Angiomax (Biogen, Inc.,Cambridge, Mass.), calcium channel blockers (such as nifedipine),colchicine, fibroblast growth factor (FGF) antagonists, fish oil (omega3-fatty acid), histamine antagonists, lovastatin (an inhibitor ofHMG-CoA reductase, a cholesterol lowering drug, brand name Mevacor(R)from Merck AND Co., Inc., Whitehouse Station, N.J.), monoclonalantibodies (such as those specific for Platelet-Derived Growth Factor(PDGF) receptors), nitroprusside, phosphodiesterase inhibitors,prostaglandin inhibitors, suramin, serotonin blockers, steroids,thioprotease inhibitors, triazolopyrimidine (a PDGF antagonist), superoxide dismutases, super oxide dismutase mimetic,4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl (4-amino-TEMPO), estradiol,anticancer agents, dietary supplements such as various vitamins, and acombination thereof. Examples of anti-inflammatory agents includingsteroidal and nonsteroidal anti-inflammatory agents include biolimus,tacrolimus, dexamethasone, clobetasol, corticosteroids or combinationsthereof. Examples of such cytostatic substances include angiopeptin,angiotensin converting enzyme inhibitors such as captopril (e.g.Capoten(R) and Capozide(R) from Bristol-Myers Squibb Co., Stamford,Conn.), cilazapril or lisinopril (e.g. Prinivil(R) and Prinzide(R) fromMerck AND Co., Inc., Whitehouse Station, N.J.). An example of anantiallergic agent is permirolast potassium. Other therapeuticsubstances or agents which may be appropriate include alpha-interferon,pimecrolimus, imatinib mesylate, midostaurin, and genetically engineeredepithelial cells.

Further examples of specific bioactive agents are neurological drugs(amphetamine, methylphenidate), alpha1 adrenoceptor antagonist(prazosin, terazosin, doxazosin, ketenserin, urapidil), alpha2 blockers(arginine, nitroglycerin), hypotensive (clonidine, methyldopa,moxonidine, hydralazine minoxidil), bradykinin, angiotensin receptorblockers (benazepril, captopril, cilazepril, enalapril, fosinopril,lisinopril, perindopril, quinapril, ramipril, trandolapril, zofenopril),angiotensin-1 blockers (candesartan, eprosartan, irbesartan, losartan,telmisartan, valsartan), endopeptidase (omapatrilate), beta2 agonists(acebutolol, atenolol, bisoprolol, celiprolol, esmodol, metoprolol,nebivolol, betaxolol), beta2 blockers (carvedilol, labetalol,oxprenolol, pindolol, propanolol) diuretic actives (chlortalidon,chlorothiazide, epitizide, hydrochlorthiazide, indapamide, amiloride,triamterene), calcium channel blockers (amlodipin, barnidipin,diltiazem, felodipin, isradipin, lacidipin, lercanidipin, nicardipin,nifedipin, nimodipin, nitrendipin, verapamil), anti arthymic active(amiodarone, solatol, diclofenac, flecainide) or ciprofloxacin,latanoprost, flucloxacillin, rapamycin and analogues and limusderivatives, paclitaxel, taxol, cyclosporine, heparin, corticosteroids(triamcinolone acetonide, dexamethasone, fluocinolone acetonide),anti-angiogenic (iRNA, VEGF antagonists: bevacizumab, ranibizumab,pegaptanib), growth factor, zinc finger transcription factor, triclosan,insulin, salbutamol, oestrogen, norcantharidin, microlidil analogues,prostaglandins, statins, chondroitinase, diketopiperazines, macrocyclicompounds, neuregulins, osteopontin, alkaloids, immuno suppressants,antibodies, avidin, biotin, clonazepam. The foregoing substances canalso be used in the form of prodrugs or co-drugs thereof. The foregoingsubstances also include metabolites thereof and/or prodrugs of themetabolites. The foregoing substances are listed by way of example andare not meant to be limiting.

In accordance with the present invention, if a bioactive agent ispresent, the concentration of one or more bioactive agent(s) in thefibers can be determined by the therapeutic window of the treatedmedical indication as well as by an administration method. Theconcentration of one or more bioactive agent(s) in the fibers, can be atleast 1 wt %, based on the total weight of the fibers, in particular atleast 5 wt. %, more in particular at least 10 wt %. The concentrationmay be up to 90 wt %, up to 70 wt %, up to 50 wt. % or up to 30 wt. %,as desired.

In addition to the biodegradable polyesteramides as represented byformula IV, the fibers of the present invention may further comprise oneor more other polymers selected from the group of biocompatiblepolymers.

Examples of biocompatible polymers are poly(ortho esters),poly(anhydrides), poly(D,L-lactic acid), poly (L-lactic acid),poly(glycolic acid), copolymers of poly(lactic) and glycolic acid,poly(L-lactide), poly(D,L-lactide), poly(glycolide),poly(D,L-lactide-co-glycolide), poly(L-lactide-co-glycolide),poly(phospho esters), poly(trimethylene carbonate), poly(oxa-esters),poly(oxa-amides), poly(ethylene carbonate), poly(propylene carbonate),poly(phosphoesters), poly(phosphazenes), poly(tyrosine derivedcarbonates), poly(tyrosine derived arylates), poly(tyrosine derivediminocarbonates), copolymers of these polymers with poly(ethyleneglycol) (PEG), or combinations thereof.

The fiber is preferably manufactured via an extrusion process forexample melt extrusion in which the biodegradable polymer and eventualadditional compounds are homogenized using a Retsch cryomill. Theresulting powder is then filled into a pre-heated DSM Xploremicro-extruder with 5 cc barrel size and twin-screws which are connectedto a micro fiber spin device. The biodegradable polymer preferably has aresidence time of 5-10 min at 120 C-140° C. before it is to be stretchedinto a fiber with diameter in the range of 100-250 μm. The extrusion isnormally performed under inert atmosphere in order to minimize theoxidative degradation of the polymer during the process. Under tensionit is subsequently cooled at room temperature. The obtained fiber isthen preferably cut into pieces from for example 4 mm and may besterilized via gamma radiation.

The fibers according to the present invention which can be obtained viaextrusion do re-model upon exposure to aqueous environment reducingsignificantly their length and increasing in diameter. The total volumeof the fibers is preserved. The length of the fiber is typically reducedby factor of 2 to 20.

Alternatively the fibers of the present invention can also be preparedvia injection moulding. In this process fibers are formed in aninjection moulder at temperature between 50-200° C., preferably between100-200° C., resulting in fibers with a diameter of approximately 200μm. Then the mould is cooled to room temperature before opening and thefibers are taken out. Essential for this processing method is that soobtained fibers do not re-model upon exposure to aqueous environmentwell preserving their length and diameter.

In case that the fibers are loaded with one or more bioactive agents,the loading may be achieved by forming the fibers in the presence of thebioactive agent or thereafter. To achieve fibers with a high amount ofbioactive agent, it is generally preferred to prepare the fibers in thepresence of the bioactive agent. In particular in the case that thebioactive agent is sensitive it is preferred to load the fibers afterthey have been formed. This can be achieved by contacting the fiberswith the bioactive agent and allowing the bioactive agent to diffuseinto the fibers and/or adhere/adsorb to the surface thereof.

In accordance with the invention it is possible to provide fibers withone or more bioactive agents with satisfactory encapsulation efficiency.(i.e. the amount of bioactive agent in the fibers, divided by the amountof active agent used).

Depending upon the loading conditions, an efficiency of at least 20%, anefficiency of at least 50%, at least 75% or at least 90% or more isfeasible.

The fibers may be incorporated in for example (rapid prototyped)scaffolds, coatings, patches, composite materials, gels, plasters orhydrogels.

The fibers according to the present invention can be injected orimplanted.

In a further embodiment, the fibers may be imageable by a specifictechnique such as MRI, CT, X-ray. The imaging agent can be incorporatedinside the fibers or can be coupled onto their surface. A suitableimaging agent is for example gadolinium.

The fibers comprising the polyesteramide copolymers according to thepresent invention can be used in the medical field especially in drugdelivery in the field of management of pain, MSK, ophthalmology, cancertreatment, vaccine delivery compositions, dermatology, cardiovascularfield and orthopedics, spinal, intestinal, pulmonary, nasal, orauricular field.

The fiber according to the present invention can be used as a drugeluting vehicle especially for the treatment of disease inophthalmology.

The present invention will now be described in detail with reference tothe following non limiting examples and figures which are by way ofillustration only.

Materials

Unless specified otherwise, all chemicals were purchased fromSigma-Aldrich. 1H NMR analysis was performed on a Varian Inova 300spectrometer using a 10 mg/ml polymer solution in deuterated DMSO. Theused DSC equipment was from Mettler Toledo 822e connected with anIntercooler and an auto robot TS0801 RO.

FIGURES

FIG. 1: In vivo degradation of PEA-III-Ac Bz and PEA-III-25% H fibers.

FIG. 2: In vitro/In vivo correlation of degradation of PEA-III-Ac Bz andPEA-III-25% H fibers.

FIG. 3: Molecular weight decrease during hydrolytic degradation in PBSbuffer over 180 days

FIG. 4: Weight loss of the fibers during hydrolytic degradation in PBSbuffer over 180 days.

FIG. 5: Evaluation of form stability is graphically represented by fiberlength.

FIG. 6: In vivo degradation of PEA-III-Ac Bz and PEA-III-25% H fibersover 6 months.

FIG. 7: In vitro/In vivo correlation of degradation of PEA-III-Ac Bz andPEA-III-25% H fibers over 6 months.

FIG. 8: Molecular weight decrease during hydrolytic degradation in PBSbuffer over 266 days.

FIG. 9: Weight loss of the fibers during hydrolytic degradation in PBSbuffer over 266 days.

EXAMPLES Example 1

Fibers of PEA-III-Ac Bz, PEA-III-H/Bz 25% H and PEA-III-H/Bz 50% H wereprepared via extrusion with a diameter of approximately 180 μm. Theobtained fibers were cut into pieces with a length of 4-5 mm and wereindividually weighted on a microbalance. The single fibers were immersedin 3 mL PBS buffer containing 0.05% sodium azide as a biocide.Hydrolytic degradation was performed under gentle orbital shaking at 37°C. Samples were taken in triplicate; the fibers were dried under reducedpressure at 37° C. overnight. The weight of the fibers post degradationwas again determined with a microbalance. Relative molecular weights ofthe remaining polymer fiber were determined using a Waters GPC systemconsisting of a Waters RI detector type 2414, a Waters separation modulewith column heater type e2695. The system was equipped with a StyragelHR5E and Styragel HR2 column run at 50° C. As the mobile phasetetrahydrofuran (THF) with a flow rate of 1.0 mL/min was used. Sampleswere dissolved in 200 μl THF, of which 100 μL was injected onto thecolumn. Evaluation of data was performed with Waters Empower² software.Calculations of molecular weights were relatively to polystyrenestandards. Results are represented in FIGS. 3 and 8 which show molecularweight decrease during hydrolytic degradation in PBS buffer over 180days and 266 days respectively. FIGS. 4 and 9 show the weight loss ofthe fibers during hydrolytic degradation in PBS buffer over 180 days andover 266 days respectively.

Example 2

The polymers applied were synthesized via polycondensation ofpre-calculated amounts of di-p-toluenesulfonicacid salts ofbis-(L-leucine) 1,4-dianhydro sorbitol diester, bis-(L-leucine)α,ω-hexane dioldiester, lysine benzyl ester, lysine anddi-N-hydroxysuccineimid ester of sebacic acid in anhydrous DMSO andtriethylamine added in a glass vessel with overhead stirrer under anitrogen atmosphere. The usage of pre-activated acid in the reactionallows polymerization at relatively low temperature (65 C; 48 h)affording side-products free polycondensated and predictable degradationproducts. The polymers were isolated from the reaction mixture in twoprecipitation steps to result in white amorphous material of averagenumber molecular weight of 50 kDa as determined by THF based GPCrelative to polystyrene standards. The ratio of the different buildingblocks in the polymer was calculated from the 1H NMR spectrum.Co-polymer composition matched well theoretical prediction. Next thepolymers were cryomilled in Retsch ZM200 equipment in presence of 0.20%w/w Chromoionophore II in order to obtain a uniform mixture.

The uniformed cryomilled formulation was processed to fibres at thePharma mini-extruder with a speed of 1-250 rpm, a temperature range of140 C, equipped with DSM micro fiber spin device for thin fiberspinning. The polymer had a residence time of 5-10 min at 140 C beforeto be stretched into a fiber with diameter in the range of 120-300 μm.The extrusion was performed under inert atmosphere in order to minimizethe oxidative degradation of the polymer during the process. Theobtained fiber was cut to about 4 mm long and 150 μm in diameter piecesand sterilized via gamma radiation 25 kGy under cooling conditions atBGS, Wiehl, Germany.

Implantation and Clinical Follow Up

Female Chinchilla Bastard rabbits (Charles River Company, Sulzfeld,Germany) with an average body weight of 2-3 kg were used. All animalexperiments were conducted in accordance with the principles for thecare and use of research animals and were carried out with permissionand supervision of the Office for the Nature, Environment and ConsumerProtection (LANUV), Recklinghausen, Germany.

For subconjunctival implantation a radial incision was made into therabbit conjunctiva and a chamber was prepared by dissecting theconjunctiva from the sclera. One dry fiber was placed into the chamberand the incision was closed with one vicryl 9-0 suture. One sample ofPEA per eye was implanted. The implant was monitored weekly andread-outs were scheduled after one, three, six, and twelve months.

For intravitreal implantation of dry fibers a customized 26 Gintravenous catheter was used. A transscleral paracenthesis was madewith a 26 G needle 1.5 mm below the limbus and the modified catheter wasinserted. After removing the catheter needle the PEA fiber was insertedto the catheter with a micro forceps and moved forward with the catheterneedle into the vitreous. The catheter was removed and the intravitrealposition of the fiber was documented by video photography. PEA fiberswere explanted after 1 and 3 months. Clinical examinations by funduscopywere done weekly to confirm presence and shape of the fibrils and toobserve status of the fundus.

After mentioned observation periods eyes were enucleated andmacroscopically analyzed. In addition, the explanted fibers wereevaluated by weight and GPC in order to assess the changes occurringwith the polymer.

Implantation and Clinical Follow Up

Female Chinchilla Bastard rabbits (Charles River Company, Sulzfeld,Germany) with an average body weight of 2-3 kg were used. All animalexperiments were conducted in accordance with the principles for thecare and use of research animals and were carried out with permissionand supervision of the Office for the Nature, Environment and ConsumerProtection (LANUV), Recklinghausen, Germany.

For subconjunctival implantation a radial incision was made into therabbit conjunctiva and a chamber was prepared by dissecting theconjunctiva from the sclera. One dry fiber was placed into the chamberand the incision was closed with one vicryl 9-0 suture. One sample ofPEA per eye was implanted. The implant was monitored weekly andread-outs were scheduled after one, three, six, and twelve months.

For intravitreal implantation of dry fibers a customized 26 Gintravenous catheter was used. A transscleral paracenthesis was madewith a 26 G needle 1.5 mm below the limbus and the modified catheter wasinserted. After removing the catheter needle the PEA fiber was insertedto the catheter with a micro forceps and moved forward with the catheterneedle into the vitreous. The catheter was removed and the intravitrealposition of the fiber was documented by video photography. PEA fiberswere explanted after 1 and 3 months. Clinical examinations by funduscopywere done weekly to confirm presence and shape of the fibers and toobserve status of the fundus.

After mentioned observation periods eyes were enucleated andmacroscopically analyzed. In addition, the explanted fibers wereevaluated by weight and GPC in order to assess the changes occurringwith the polymer.

Example 3

Fibers of PEA-III-H/Bz 25% H were prepared via injection moulding with adiameter of approximately 200 μm. The obtained fibers were cut intopieces with a length of 5-10 mm and were individually weighted on amicrobalance. Each individual fiber was imaged using a Motic stereoscopeequipped with a Moticam2000 digital camera.

Single fibers were immersed in 1 mL PBS buffer and placed on a gentleorbital shaker at 37° C. The experiment was performed in duplicate. Atgiven time points, fibers were gently removed from the buffer andblotted on tissue. Images were taken with the stereoscope and the fiberlength and diameter were measured. Buffer was refreshed and the sampleswere returned to the orbital shaker. In FIG. 5 a calculation of formstability is graphically represented by measuring fiber length. Theinjection moulded fibers had an initial length of 10 mm and the extrudedfiber had initial length of 5 mm. Differences in form stability areclearly expressed by the loss in length of the extruded fiber.

1. Fibers comprising a biodegradable poly(esteramide) random copolymer(PEA) according to structural formula (IV),

wherein m+p varies from 0.9-0.1 and q varies from 0.1 to 0.9 m+p+q=1whereby m or p could be 0 n varies from 5 to 300; —R₁ is independentlyselected from the group consisting of (C₂-C₂₀) alkylene or (C₂-C₂₀)alkenylene and combinations thereof; —R₃ and R₄ in a single backboneunit m or p, respectively, are independently selected from the groupconsisting of hydrogen, (C₁-C₆)alkyl, (C₂-C₆)alkenyl, (C₂-C₆)alkynyl,(C₆-C₁₀)aryl, (C₁-C₆)alkyl, —(CH₂)SH, —(CH₂)₂S(CH₃), —CH₂OH, —CH(OH)CH₃,—(CH₂)₄NH₃+, —(CH₂)₃NHC(═NH₂+)NH₂, —CH₂COOH, —(CH₂)COOH, —CH₂—CO—NH₂,—CH₂CH₂—CO—NH₂, — —CH₂CH₂COOH, CH₃—CH₂—CH(CH₃)—, (CH₃)₂—CH—CH₂—,H₂N—(CH₂)₄—, Ph-CH₂—, CH═C—CH₂—, HO-p-Ph-CH₂—, (CH₃)₂—CH—, Ph-NH—,NH—(CH₂)₃—C—, NH—CH═N—CH═C—CH₂—. —R₅ is selected from the groupconsisting of (C₂-C₂₀)alkylene, (C₂-C₂₀)alkenylene, alkyloxy oroligoethyleneglycol —R₆ is selected from bicyclic-fragments of1,4:3,6-dianhydrohexitols of structural formula (III), cycloalkylfragments, aromatic fragments or heterocyclic fragments.

—R₇ is selected from the group consisting of (C₆-C₁₀) aryl (C₁-C₆)alkyl—R₈ is —(CH₂)₄ whereby a is at least 0.05, b is at least 0.05 and a+b=1.2. Fibers comprising a polyesteramide copolymer according to claim 1 inwhich a is at least 0.5.
 3. Fibers comprising a polyesteramide copolymeraccording to claim 1 in which a is at least 0.75.
 4. Fibers comprising apolyesteramide copolymer according to claim 1 wherein p=0 and m+q=1,m=0.75, a is 0.5 and a+b=1. R₁ is (CH₂)₈, R₃ is (CH₃)₂—CH—CH₂—, R₅ ishexyl, R₇ is benzyl, R₈ is —(CH₂)₄—.
 5. Fibers comprising apolyesteramide copolymer according to claim 1 wherein m+p+q=1, q=0.25,p=0.45 and m=0.3, a is 0.5 and a+b=1; R₁ —(CH₂)₈; R₃ and R₄respectively, are (CH₃)₂—CH—CH₂—, R₅ is selected from the groupconsisting of (C₂-C₂₀)alkylene, R₇ is benzyl, R₈ is —(CH₂)₄; R₆ isselected from bicyclic-fragments of 1,4:3,6-dianhydrohexitols ofstructural formula (III).
 6. Fibers comprising a polyesteramidecopolymer according to claim 1 wherein: m+p+q=1, q=0.25, p=0.45 andm=0.3 a=0.75, a+b=1 R₁ is —(CH₂)₈; R₄ is (CH₃)₂—CH—CH₂—, R₇ is benzyl,R₈ is —(CH₂)₄; R₆ is selected from bicyclic-fragments of1,4:3,6-dianhydrohexitols of structural formula (III).
 7. Fiberscomprising a polyesteramide copolymer according to claim 1 wherein:m+p+q=1, q=0.1, p=0.30 and m=0.6 a is 0.5 and a+b=1 R₁ —(CH₂)₄; R₃ andR₄ respectively, are (CH₃)₂—CH—CH₂—; R₇ benzyl, R₈ is —(CH₂)₄—; R₅ isselected from the group consisting of (C₂-C₂₀)alkylene, R₆ is selectedfrom bicyclic-fragments of 1,4:3,6-dianhydrohexitols of structuralformula (III), cycloalkyl fragments, aromatic fragments or heterocyclicfragments.
 8. Fibers according to claim 1 with an average diameter inthe range of 50-1000 μm.
 9. Fibers according to claim 1 comprising abioactive agent.
 10. Fibers according to claim 1 for use as amedicament.
 11. Use of the fibers according to claim 1 in drug deliveryapplications.
 12. Use of the fibers according to claim 1 in ophthalmicapplications.
 13. Method for the preparation of the fibers according toclaim 1 via melt extrusion.
 14. Method for the preparation of the fibersaccording to claim 1 via injection moulding.